KR100450903B1 - Optimal cut psaw device and the method - Google Patents

Abstract

The present invention is directed to an optimally cut PSAW device and method. An optimally cut PSAW device in accordance with the disclosed subject matter includes a languasite substrate having a PSAW propagation surface; It consists of an input and output interdigital transducer with on-surface electrodes for generating and detecting surface acoustic waves on the substrate, wherein one surface wave direction of propagation is along the X 'axis, and the substrate is Z perpendicular to the surface. 'An axis and along the surface and having a Y' axis that is perpendicular to the X 'axis, wherein the rangasite surface has a crystal orientation defined by crystal axes X, Y and Z, and axes X', Y 'and Z Is characterized by the Euler angles φ, θ, and ψ, where φ is in the range of 0 °, θ is 12 ° -17 °, and ψ is 73 ° -78 °. .

The optimally cut PSAW device and method according to the present invention can provide a PSAW device having optimal parameter characteristics by applying the optimal cutting Euler angle value of the LGS substrate to make good use of the characteristics of the PSAW.

Description

OPTIMAL CUT PSAW DEVICE AND THE METHOD

The present invention relates to an optimally cut PSAW device and method, and in particular, to provide an optimal cutting azimuth angle of single crystal lanthanum gallium silicate, called Langasite (LSG: La ₃ Ga ₅ SiO ₁₄ ) of a PSAW device, thereby providing an optimal parameter. An optimally cut PSAW apparatus and method are disclosed.

In recent years, mobile communication uses radio waves to enable communication with mobile objects such as automobiles, trains, or people moving when going out, and as a means, the demand has increased rapidly in the world. In order to enable such a mobile communication, it is very important to reduce the weight, low power consumption, and high functionality of the terminal, which directly serves as an interface with a user as well as a network system.

The most contributing factor to the miniaturization of such mobile phones is the miniaturization of components. In particular, SAW devices, which are representative high frequency components, are currently used as band pass filters, resonators, delay lines, and conververs in a wide range of RF and IF applications such as wireless, cellular communication, and cable TV.

In the case of the dielectric duplexer, a size of about 1.2cc has been recently developed and will continue to be miniaturized later. However, in the case of ultra-thin mobile phones, there is a movement to adopt some SAW duplexers. This is because the SAW duplexer filter plays a decisive role in reducing the volume and weight of the mobile phone.

In general, the SAW duplexer filter is used as a band pass filter, which includes a horizontal SAW filter having two interdigital transducers (IDTs) arranged at a predetermined distance on a piezoelectric substrate, and a resonator constituting a resonator on the piezoelectric substrate. Filters are known.

As the SAW resonator filter, there is a sectional reflection type SAW resonator filter using shear horizontal surface acoustic waves such as love waves, Bleustein-Gulyaev-Shimuzu (BGS) waves, and other similar waves.

In order to develop the SAW duplexer, electrode design technology, pattern manufacturing technology, SMD packaging technology, high frequency characteristic measurement technology, and impedance matching circuit design technology should be systematically organized.

SAW substrates generally used in pattern fabrication techniques include lithium niobate, ST crystal and lithium tantalite. Here, in order to apply the substrates to the SAW filter, it is necessary to cut a substrate by determining a specific orientation according to various characteristics.

These characteristics include SAW velocity, SAW pressure coupling coefficient, power flow angle, diffraction or light spreading coefficient, Y (gamma), temperature delay coefficient and TCD. Therefore, the SAW device is generally used as a device for obtaining high frequency due to the good characteristics.

On the other hand, PSAW (Pseudo SAW) device is recently used as an element to obtain a high frequency because the phase velocity (phase velocity) is faster than the SAW device. Therefore, it is important to select and cut a languisite substrate in an optimal orientation to optimize the characteristics of the PSAW device.

However, when the substrate applied to the PSAW device falls below a basically required value, a problem arises in that the characteristics of the PSAW device are changed.

The present invention was created to improve the above problems, to provide an optimal cut PSAW device and method having the characteristics of the optimum parameters by applying the ideal cutting Euler angle value of the LGS substrate to make good use of the characteristics of the PSAW. The purpose is.

1 is a view showing the minimum dielectric loss when the Euler angle φ = 0 of the PSAW langaceite according to the present invention.

2 is a diagram illustrating a general Euler angle.

In order to achieve the above object, an optimally cut PSAW device according to the present invention,

A langasite substrate having a PSAW propagation surface;

It consists of an input and output interdigital transducer having on-surface electrodes for generating and detecting surface acoustic waves on the substrate, wherein one surface wave direction of radio waves exists along the X 'axis, and the substrate is Z perpendicular to the surface. 'An axis and along the surface and having a Y' axis that is perpendicular to the X 'axis, wherein the rangasite surface has a crystal orientation defined by crystal axes X, Y and Z, and axes X', Y 'and Z Is characterized by the Euler angles φ, θ, and ψ, where φ is in the range of 0 °, θ is 12 ° -17 °, and ψ is 73 ° -78 °. .

In addition, the optimal cut PSAW method according to the present invention to achieve the above object,

Defining a crystal orientation in which the languasite surface with PSAW propagation is defined by the crystal axes X, Y, and Z;

Defining a surface wave direction of the propagation along an X 'axis, wherein the substrate defines a Z' axis perpendicular to the surface wave and a Y 'axis along the surface and perpendicular to the X' axis;

Defining the axes X ', Y', Z 'as the relative azimuth Euler angles φ, θ, and ψ of the crystals;

It is characterized in that it includes the step of defining that φ is 0 °, θ is 12 °-17 °, ψ has a value of 73 °-78 °.

Here, in particular, it is characterized in that the Euler angle of the PSAW langasite is optimal when φ = 0, θ = 14.6 °, ψ = 76.2 °.

According to the present invention as described above, an optimum parameter can be obtained by applying the optimum cutting azimuth angle of single crystal lanthanum gallium silicate, which is called Langasite (LSG: La ₃ Ga ₅ SiO ₁₄ ) of the PSAW device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing the minimum loss when the Euler angle of the PSAW langaceite according to the present invention is φ = 0, θ = 14.6 °, ψ = 76.2 °. As shown therein, the minimum loss is shown when φ = 0.

Further, each parameter value calculated by the simulation of the Euler angles (0 °, 14.6. °, 76.2 °) is V _S (km / s) = 3.402727, V ₀ (km / s) = 3.04514, K2 (% ) = 0.1585, pfa (deg) = -4.556, tcd (ppm / C) = 30.176, tcd2 (1e-9 / C ^ 2) = 51.942, loss_s (㏈ / λ) = 0.0006225, loss_o (㏈ / λ) = 2.19E-05. Here, the temperature stability may be applied to the PSAW device because the stability of the temperature is not required.

Since it is quite difficult to satisfy all of the optimal values of the parameters, we apply an approximation to these values. The proposed Euler angle ranges are 0 ° for φ, 12 ° for 12 °, and 17 ° for θ. ψ is proposed as 73 ° ≤ψ≤78 °.

Meanwhile, the concept of the Euler angle will be described. 2 is a view illustrating a general Euler angle. As shown therein, the direction of SAW propagation is first parallel to X 'and then a contour of a wafer on a surface parallel to the Z' axis is plotted and flattened along one edge of the wafer perpendicular to the X 'axis. .

Then, it is assumed that the crystal axes X, Y, and Z coincide with the wafer axes X ', Y', and Z ', respectively, and if there is no rotation, the wafer is cut into a polished surface perpendicular to the Z axis. The SAW propagates in a direction parallel to the X axis.

Here, if there is any subsequent rotation, the wafer axes X ', Y', Z 'are rotated, and it is assumed that the crystal axes X, Y, Z are fixed. For example, assume that Euler angles (φ, θ, ψ) = (0, 135, 28) are close to the middle of the range, and the first rotation circumscribes Z '(from X' towards Y ') by φ. Rotation, where no rotation occurs in this case because ψ = 0.

The rotation then occurs by θ around the new X '. Here, new axes are always connected to the wafer such that any rotation takes place around the wafer axis, including all previous rotations.

Finally, we rotate around Z '(from X' towards Y ') by μ, in this case 28 °. The axes X ', Y', and Z 'are defined as the relative orientation Euler angles φ, θ, and ψ of the crystal.

Thus, for any value of each Euler angle in the proposed azimuth group it is always possible to find such a value for the other two angles, where the combination of values for the two angles results in an improved parameter characteristic. Will be provided.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the optimally cut PSAW apparatus and method according to the present invention may provide a PSAW device having an optimal parameter characteristic by applying an ideal cutting Euler angle value of the LGS substrate to make good use of the characteristics of the PSAW. .

Claims (3)

A langasite substrate having a PSAW propagation surface; It consists of an input and output interdigital transducer with on-surface electrodes for generating and detecting surface acoustic waves on the substrate, wherein one surface wave direction of propagation is along the X 'axis, and the substrate is Z perpendicular to the surface. 'An axis and along the surface and having a Y' axis that is perpendicular to the X 'axis, wherein the rangasite surface has a crystal orientation defined by crystal axes X, Y and Z, and axes X', Y 'and Z The crystal relative orientation of 'is defined by Euler angles φ, θ, and ψ, where φ is 0 °, θ is 12 ° -17 °, and ψ has a range of 73 ° -78 °. PSAW device. Defining a crystal orientation in which the languasite surface with PSAW propagation is defined by the crystal axes X, Y, and Z; Defining a surface wave direction of the propagation along an X 'axis, wherein the substrate defines a Z' axis perpendicular to the surface wave and a Y 'axis along the surface and perpendicular to the X' axis; Defining the axes X ', Y', Z 'as the relative azimuth Euler angles φ, θ, and ψ of the crystals; And wherein φ is 0 °, θ is 12 ° -17 °, and ψ is 73 ° -78 °. The method of claim 2, Optimal cut PSAW method, characterized in that the optimum when the Euler angle of the PSAW langasite is φ = 0, θ = 14.6 °, ψ = 76.2 °.